Shock-current generator employing means to effect simultaneous discharge of plural storage devices



2, 1965 R. FOlTZlK ETAL 3,163,701

SHOCK-CURRENT GENERATOR EMPLOYING MEANS T0 EFFECT SIMULTANEOUS DISCHARGE OF PLURAL STORAGE DEVICES Filed Nov. 50. 1960 3 Sheets-Sheet 1 1-1 4 is" I" C L f j.

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| l I i A z -1 Z l Jl 1965 R FOlTZlK ETAL 0 SHOCK-CURRENT GENERA TOR EMPLOYING MEANS TO EFFECT SIMULTANEOUS DISCHARGE OF' PLURAL. STORAGE DEVICES Filed Nov. 50, 1960 3 Sheets-Sheet 2 an Flya Feb. 2, 1965 R. FOITZIIK ETAL 3,168,701 SHOCK-CURRENT GENERATOR EMPLOYING MEANS TO EFFECT SIMULTANEOUS DISCHAR GE 0F PLURAL STORAGE DEVICES 3 Sheets-Sheet 3 Filed Nov. 30. 1960 United States Patent 3 163,701 SHOCK-CURRENT G ENERATOR EMPLOYING NKEANS TO EFFECT SIMULTANEOUS DIS- CHARGE OF PLURAL STORAGE DEVICES Rudolf Foitzik and Egon Zemann, Berlin-Siemensstadt,

Our invention relates to a generator for producing electric current pulses of extreme intensity and extremely steep wave shape. Such generators are applicable for testing purposes, investigation of plasma discharges and nuclear fusion phenomena.

In order to obtain the desired high current amplitudes, such shock generators, as a rule, are provided with a multiplicity of individual current sources, preferably capacitors, which are simultaneously switched upon the load. The simultaneous switching is effected by connecting the individual current sources, such as the individual capacitors or capacitor groups, with. the load terminals through spark-gap devices under control by auxiliary ignition means. The ignition, in most cases, is effected with the aid of an ignition pin mounted in proximity to, but insulated from, one of the electrodes of the spark gap. At the desired switching moment an ignition pulse is supplied to the ignition pins of all spark gaps. This preionizes each spark gap so that it can'flash under the effect of the operating voltage impressed between the two gap electrodes. However, even if all spark gaps receive the ignition pulses simultaneously, for example from a common ignition device, it may happen that not all of them will ignite simultaneously in the strict sense so that not all of the capacitors are discharged through the load exactly at the same moment; As a consequence, the amplitude of the current shock as well as its flank steepness are reduced and, in most cases, are not as satisfactory as expectable theoretically. l f

It is an object of our invention to more reliably achieve an increased accuracy in simultaneousness of ignition and break-through in the spark gaps correlated to the respective capacitors or other current sources in a shock-current generator of the type afore mentioned. Another, related object of our invention is to improve thedegree of utilization of the power available from the totality of individual current sources so as to increase the actually effective amplitude of the shock current as well as the steepness of the current-pulse characteristic.

To this end, and in accordance with a feature of our invention, we provide a shock-current generator of the and greater curve steepness is obtained. This is particularly advantageous in plants for research and testing work concerning the production of the so-calledpinch effect in plasma, or for the like investigations relating to nuclear fusion phenomena, where an extremely fast rise .of the current at the rate of 10 to 10 amps/ second is desirable.

Our invention is based upon the following recognition.

Since the spark gaps for switching the charged capacitors or other current sources upon the load must of necessity,

- possess a break-through voltage greater than the voltage 0f the current sources, the spark gaps do not immediately respond to the ignition effected by the ignition devices. The break-through rather takes place with a discharge delay in the order of 10- to 10 second. This delay is not constant but differs among the respective spark gaps. It is virtually inevitable that one of the spark gaps will break through earlier than all others. When the current source whose spark gap is thus switched-on ahead of the others, becomes discharged through the load, the negligibly small resistance of the conductors between current source and load causes substantially the entire voltage of the current source to be impressed upon the load. This has the consequence that the voltage at the other spark gaps of the parallel-connected current sources is instantaneously reduced to the zero value." Hence, the spark gaps of the, other parallel-connected current sources cannot fire. The firing of these spark gaps takes place only after the voltage imposed upon the load by the firstswitching current source has decayed to such an extent that again a higher voltage occurs across the other spark gaps. In many cases, however, only one of (the other spark gaps will then ignite first. Consequently, only a portion of the other current sources will next become discharged. The performance therefore progresses in cascade or chain fashion.

The provision of an auxiliary voltage source according to the invention as briefly outlined above, has the effect that the first discharging current source does not impose too high a voltage uponthe load] The auxiliary voltage source ofopposed polarity keeps the voltage at the load so low that a voltage sufficient for ignition remains available at the spark gaps of the other current sources. Although thishas the consequence that the power of the first-switching current source is partially lost for the intended purpose, such loss is negligible because all other spark gaps can now ignite without delay, thus securing a considerably higher rate of current rise and current amplitude than attainable With the shock-current generators heretofore available.

According to another feature of our invention, the justmentioned power loss of the first-switching source can be kept extremely slight by using as auxiliary voltage source a capacitor which is charged to a voltage higher than that of the current sources. In this case, a very small capacitance value for the auxiliary voltage source is sufficient, which can take up only an extremely slight fraction of the energy available in the current sources.

According to still another feature, the auxiliary voltage source is composed of a plurality of capacitors arranged symmetrically with respect to the load. This is particularly advantageous in cases where only little space is available at the load so that a large capacitor cannot readily be accommodated. The symmetrical arrangement of voltage-supplying auxiliary capacitors is also of advantage in many cases because the discharge phenomena in such shock-current generators occur with such extreme rapidity that the travelling-wave periods of the conductors must be taken into account.

' According to another, preferred feature of ourinvention, the auxiliary voltage source is connected to the load in such time relation to the firing of thevabove-mentioned spark gaps that the auxiliary voltage becomes effective just prior to the ignition of the spark gaps. As a result, a high voltage is impressed across the spark gaps before any of them is ignited to effect discharge of the appertaining currentsource.

For example, the provision of an auxiliary voltage source having a voltage equal to that of the current sources, increases the shock factor of the switching spark gaps from less than the value 1 up to about 2. The shock factor is the ratio of the voltage impressed upon a spark gap at the ignition moment relative to the static.

. discharge delay, i.e. the time elapsing between the application of the voltage and the breakthrough of the spark gaps, in turn results in improving the degree of simultaneousncss of ignition in all spark gaps of the respective current sources. I

V Preferably, the difference in time between theactivation of the voltage source and the ignition of the spark gaps is so chosen that the source voltage appears across the spark gaps as accurately aspossible at the same moment at which the ignition pulse required for firing the spark gap reaches the ignition pins. With theusual dimensions of such shock-current generators, this time interval amounts to approximately second. The auxiliary voltage should notbecome effective after the ignition pulse has arrived at the spark gaps. On the otherhand, the auxiliary voltage should not become effective too early before the arrival of the ignition pulse becausethen, under I certain circumstances, the spark gaps may become ignited by the effect of the auxiliary voltage alone. Since the shock factoris still relatively small (approximately 2), such premature ignition would be accompanied by excessive stray between the ignition moments of the respective spark gaps and thus would interfere with the desired high degree of simultaneousness.

According to still another feature of our invention it is preferable to switch the auxiliary voltage source, like the current sources, by means of a spark gap under control by an auxiliary ignition device. Injthis case, thespark gap of the auxiliary voltage source and the spark gaps of the ,justable manner by providing for different travelling-wave periods of the conductors that supply the ignition pulses to theindividual spark gaps.

The simultaneousness of ignition inshock-current generators according to the invention can be further improved by having two adjacent spark gaps of respective current ,sources interconnected by a conductor, possessing a travelling-wave period about equal to the average discharge delay of about'10- second, for example. Such a discharge delay in the order of l0- second applies to a spark .gap with auxiliary ignition device for a shock factor of approximatelyl. Hence, ifadjacent spark gaps are connected with cach'other by a conductor whose travellingwave period is in the same order as the discharge delay, any premature discharge of a current source through a spark gap cannot yet reduce the voltage across the ad- .jacent gap within the critical interval of time. Such a conductor with a Wave propagationperiod in the order of 10* second can readily be provided in shock-current generators where the current sources are mounted remote from the load, for example where the load lies in the center of a circular arrangement of current sources. In such a generator the spark gaps may be arranged directly 'at the respective currentsources so that twice the length of the radial conductor between a current source and the load is available between each two adjacent spark gaps. With the usual dimensions of shock-current generators, this length suffices for obtaining a travelling-wave period of 10" second. V V

The foregoing and more specific erator. a e

v objects, advantages "and features'ofour invention, said features being set forth with particularity in the claims annexed hereto, will be view of the shock-current genand are all connected in parallel. They are charged from a suitable voltage source through respective resistors R R 3R R as will be more fully described with reference to FIG. 4. The load is represented for example by an electronic discharge 'vessel G for observation of ultra-high temperature or nuclear-fusion phenomena. i

Each main capacitor is connected in series with a spark gap device FS PS by means of which the capacitors C to C are to be simultaneously switched'upon the load G. Each spark gap device comprises two electrodes at and b. Mounted in each electrode b and insulated therefrom is an auxiliary ignitionpin 0. Each pin 0 is connectedby a lead L with an ignition device, de-

scribed hereinafter, which furnishes' an ignition pulse at.

the switching moment. The ignition pulse causes a-breakthrough between the ignition pin c and the electrode b so that the spark gap between the electrodes a and b becomes pre-ionized, thus firing each gap for simultaneously discharging the parallel-connected capacitors C to C through the load. G. One of the two bus conductors L, is grounded at E.

The shock-current generator is further provided with an auxiliary voltage source which, in the illustrated'embodiment, is constituted by an auxiliary capacitor C This capacitor is charged through a resistor R, by voltage -whose polarity is opposed to thatof the main capacitors,

this being apparent from the plus and minus signs entered in FIG. 1. The auxiliary. capacitor C is likewise provided with a spark gap device FS comprising two electrodes a, b and an ignition pin 0. The control lead L of the ignition pin is connected to the'same ignition device as the control leads L of the spark gaps PS to FS As shown in FIGS. 4 and 5 the load, constituted by 'the discharge vessel G, is located on a circular carrier 1 in the center of the circular. group of capacitors C to C5,

the power electrode 2 of vessel G being directly joined mechanically and electrically with the center structure l.

.The upper electrode 3 is connected to an intermediate conductor piece 4 which forms a hood around the discharge vessel and electrically connects the electrode 3 with an annular conducting disc 5 mounted above the center structure 1 and insulated therefrom at 6.

The main capacitors C to C are'arranged in groups of four, with two of the four capacitor units 10 to 13in each group mounted beside each other (10, 11 or 12, 13) and two mounted one above the other (10, 12 or 11, 13). Placed between the capacitor groups are sheet metal boxes 14 filled with sand and having a pointed wedge-like shape. so that the circular arrangement apparent from FIG. 5 is obtained. A single charging resistor R to ll is provided Each charging resistor is fastened to a busconductor L of circular shape which extends along and above the capacitor groups. The bus L,, is connected with a source 16 of charging voltage still to be described. I

The main capacitors C to c, are supported by insulators 17, with the housings of the capacitors under voltage relative to ground. The capacitor housings of each group are connected with the center structure 1 by a 'tubular conductor 20. Mounted in the tubular conductor 20at the end adjacent to' the capacitors, is a spark gap device ES. The electrodes a and b ofthe spark gap device FS form part of the tubular 'conductor 20. They aresurrounded by an insulatingtube 21. :Asecond tubu-' lar conductor 22 extends concentrically to the tubular conductor 20 and is separated therefrom by an insulating layer 23. One end of the tubular conductor 22 is connected through an annular plate 24 with the in-lead bushings 18 of the capacitor group. The other end of tubular conductor 22 is connected to the annular disc 5. The conductors L (FIGS. 1, 2) are thus designed as a coaxial structure constituted by the inner conductor 20 and the outer conductor 22. The ignition lead L (FIGS. 1, 2) which connects the auxiliary ignition pin of the spark gap device FS with ignition device 25 is likewise designed as a coaxial cable.

Two auxiliary capacitors C and C are mounted beside the discharge vessel G above the annular disc and are electrically connected between the center structure 1 and the annular disc 5 by a coaxial conductor L (FIG. 4)

corresponding to the individual leads L shown in FIG. 1. The two capacitors C and C thus are connected in parallel relation to the discharge vessel G. A spark gap device PS is disposed in the coaxial conductor L and has its ignition pin c connected to the ignition device 25 through a coaxial conductor L The two capacitors C and C' are located in symmetrical relation to the load G and to the main capacitors C to C and are electrically connected with the voltage source 16 through a charging resistor R The voltage source 16 comprises a transformer whose low-voltage primary winding 30 is energized from a utility line, for example of 220 volts. The high-voltage secondary winding 31 has one terminal grounded at 32.

The other terminal is connected with two diodes 33, 34 in anti-parallel relation to each other. The rectifier 33 is connected to the charging bus L,,, the rectifier 34 is connected to the charging resistor R of the auxiliary capacitors C G The auxiliary capacitors C C' are charged relative to ground potential by a voltage whose polarity vis inverse to that of the main capacitor C to C The ignition device 25 comprises a capacitor 40 which has one electrode grounded at 41. The capacitor 40 is charged from a transformer 42 through a rectifier 43 and a charging resistor 44. The low-voltage primary winding of transformer 42 may be energized from a utility line of 220 volts, for example. The other electrode 40 is connected through a spark gap 45 with an ignition bus 46. The spark gap 45 has an auxiliary ignition pin 41. Connected between the ignition pin 47 and the electrode 48 Whichsurrounds the pin 47, is the high-voltage winding 49 of an ignition coil. The low-voltage winding 50 of the ignition coil is connected with a capacitor 51 which is charged through a charging resistor 52 and a rectifier 53 by a voltage of 220 volts, for example. A normally open switch 55 is connected parallel to the low-voltage winding 50 and the capacitor 51. Closing of switch 55 causes the capacitor 51 to discharge through the winding 50, This induces in the high-voltage winding 49 a voltage which causes a flash-over between the electrodes 47 and 48 of the spark gap device 45. This causes firing of the spark gap 45 so that the capacitor 49 is switched onto the ignition bus 46; The bus 46 passes the ignition pulse through the coaxial conductors L or L and L to the spark gap of the main capacitors C to C as well as to the spark gap of the auxiliary capacitors C and C' The jackets of the coaxial conductors are grounded at E.

The conductors L and L are identical coaxial conductors. Care is taken, however, that the length of the conductor L is greater than that of the conductors L or U This has the consequence that the ignition pulse reaches the spark gaps PS and FS' more rapidly than the spark gaps PS to PS The performance of the above-described shock-current generator according to the invention will be further explained with reference to FIG. 2 in which the ordinate represents voltage U and the abscissa represents time t.

The straight horizontal line U represents the charging voltage of the current sources, i.e. of the capacitors the half-wave period is at least l-10 second.

' is so chosen that at the moment when '6 C to C The capacitor C serving as an auxiliary voltage source has approximately the same voltage U but of inverse polarity.

If all capacitors are to be simultaneously switched upon the load G by ignition of the spark gaps PS to FS and PS the follow-ingwill result. Due to the inevitable temporal stray in response of the respective spark gaps, caused by the discharge delay, only one spark gap will be ignited first, for example the spark gap PS Initially therefore, only the capacitor C will discharge through the load G. This causes the load voltage to decline as typified by the curve portion U Hence, the electrodes a and b of the other spark gaps PS to FS would now be impressed only by the difference voltage Despite any excitation of the ignition pin 0, this difierence voltage would not be sutficient for firing the spark gaps.

However, due to the auxiliary capacitor C provided in accordance with our invention, the voltage U is at first compensated. That is, the discharge of the capacitor C corresponding to the voltage curve shown at U by a broken line, causes the load G to be subjected to the voltage U indicated in FIG. 2 by a heavy line, As is apparent from FIG. 2, the spark gaps PS to PS are now subjected to the considerably higher difierence voltage AU=U U The data of the capacitor C and the appertaining discharge circuit comprising the leads L as shown in FIG. 1 can readily be so chosen that the voltage U will remain sulficiently small during a period of time required for firing all spark' gaps PS to PS For example, the auxiliary capacitors C and C may have a capacitance of 5,uf. The capacitance of capacitors C to C however,

'may be greater, for example 10 at. The charging voltage is the same for all capacitors, amounting to 30 kv. for example, except that capacitors C to C are charged at inverse voltage polarity relating to capacitors C and C' The inductivity of the connecting lead L L between the capacitors C and 0' and the discharge vessel G amounts to more than 20 nHenry. This results in a natural frequency of less than 500 kilocycles per second. Therefore, the voltage of the capacitor remains available at the load for a sulficiently long period of time, since If, for example, the spark gaps have a maximum discharge delay of t =10- second, the voltage U during interval r remains sufiiciently small and hence the voltage 1 also be composed of a plurality of parallel connected capacitors as is shown in FIG. 4. In the latter case, care must be taken that the discharges of all auxiliary capacitors occur simultaneously. For this purpose, the auxiliary capacitors are symmetrically distributed to prevent the occurrence of different discharge moments due to differently long wave-travelling times in the conductors L It is particularly favorable if the auxiliary voltage source is connected to the load G prior to igniting the spark gaps F5 to FS The performance of such an apparatus is apparent from FIG. 3 representing the voltage at the spark gaps PS to FS versus time.

The ignition of the spark gap FS occurs at the moment i=0. This is an interval 1 earlier than the ignition moments of the spark gaps FS to P8,,. The interval t the ignition pulse reaches the ignition pins c of the spark gaps FS to PS the electrodes a, b are subjected --to the voltage U 'whose' polarityis opposed to that of the capacitor voltage U,,. As a result, the sparkgaps F3 to P5,, are impressed by the total voltage AU: U U Even if the voltage -U is equal to the voltage U a shock factor of approximately 2 is obtained instead of the heretofore obtainable shock factor below the unity value. By virtue of the increased shock factor, a considerable shortening of the discharge delay is obtained with a-corresponding improvement in simultaneousness of ignition. The ionization of the spark gaps PS to FS 'caused 'by the ignition pulse 1 is accompanied by a discharge delay At==10? second of such a short duration that the requirement for simultaneous ignition is more perfectly satisfied than heretofore possible. The shock current closely approaches the rate'ot current rise and amplitude of the theoretically calculated sum values. By increasing the charging voltage U beyond the value U, the degree of simultaneousness can be further improved. It is essential that this does not require an appreciable additional power supply. After igniting the spark gaps PS to P8,,, the

voltage U drops down to the arc voltage of the load.

' The time interval t in the shock-current generators heretofore available, amounts to approximately 10- second. This time difference can be attained, for example, by having the spark gaps PS and the spark gaps F8; to FS, ignited by the'same ignition device and giving the ignition conductors L leading to the spark gaps PS to FS a higher travelling-wave period than the ignition lead L of the spark gap FS For this purpose, it isgenerally preferable to use conductors of the same design,

I differing from each other only in length. However-,the

different travelling-wave period can also be obtained by using respective conductors of different designs.

7 In plants where the main capacitors C to C cannot be installed directly at the load G but must be located at some distance therefrom, it is further of advantage to mount the spark gaps PS to PS directly at the current sources, namely at the main capacitorsC to C asjillustrated in FIG. 4. In contrast to the schematic representation in FIG. 1, the spark gaps then are interconnected by the coaxial connecting lines L extending between the capacitors C to C and the load 6. For example, the

line L between the capacitors C to C and the center structure 1 may have a length of 0.75 in. The tube 23. in this case may have-an outer diameter of 10 cm., and wall thickness of 1 mm., the thickness of the insulation between tubes 22 and 23 being 1-to 2 mm. Such a coaxial line has a travelling-wave velocity of about one half the speed of light, or 150,000 -km., per second. Since twice the length of the line L extends between two spark gaps PS; to FS if the spark. gaps as shown in FIG. 4 are located in proximity of the respective capacitors C to C the ignition of one spark gap can make itself felt at the other spark gaps only after the wave has travelled a distance of 2X0.75=l.5 rn. length of conductor line. Hence, with a travelling velocity of 1.5 rIL/IO- second,

an interval of 1.10' second will lapse before the ignition of one gap will affect the electrode voltage across another gap. As explained, this has the advantage that a premature discharge of a current source can aitect adjacent spark gaps only after thejust-mentioned interval of time. I Consequently, the other spark gaps atvthe moment of ,premature switching in a spark gap, remain at first suberating plants equipped with other types of current and 8 voltage sources, for example, with synchronously operating alternating-current shock generators which form the current sources to be switched simultaneously "Also suitable as source of auxiliary voltage are batterie s, for example. In this case a rapidly acting'switch maybe used for connecting the voltage to the load only for the desired short interval'of time.

It will be obvious to thoseskilled in the art, upon a study of this disclosure, that such and other modifications of our invention can readily be made without'departing from the essential features of our invention and within the scope of the claims annexed hereto.

We claim: a V a 1. A shock-current generator, comprising'amultiplicity of surge-current sources, load terminals to which said current sources are connected inparallel relation to each other with the same respective voltage polarities, normally open current control means having respective spark gaps interposed between said respective currentsources and said terminals and having ignition means for simultaneously igniting said spark gaps to simultaneously switch said current sources onto said load terminals to jointly produce a shock current when a load is connected to said terminals, a voltage source connected across said load terminals, said control means comprising switching means interposed between said voltage source and said terminals for impressing the voltage of said voltage source across said terminals when said current sources are being switched onto said terminals, said voltage sourcehaving at said terminals a voltage polarity opposed to that of said current sources. V

2. A shock-current generator, comprising a multiplicity of main capacitors andmeans for charging them to serve as surge-current source s, load terminals to which said main capacitors are connected in parallel relation to each other with the same respective voltage polarities, normally open current control means having respective spark gaps interposed between said respective main capacitors and said terminals and havingignition means torsimultane ously igniting said spark gaps. to discharge said main capacitors for jointly producing an impact current pulse when a load is connected to said terminals, a voltage source connected across said terminals and comprising an auxlliary capacitor, said control means comprising switching means interposed between said auxiliary capacitor and said terminals for impressing the voltage of said auxiliary capacitor across said terminals when said main capacitors are being discharged, said auxiliary capacitors having relative to said terminals a voltage polarity opposed to that of said maincapacitors.

3. A shock-current generator, comprising a. load, ,a multiplicity of capacitor means connected to said load in 'parallel relation to each other to serve as surge-current sources, current supply means for charging said capacitor means, said capacitor means each includinga capacitor and spark-gap devices interposed between said load and said respective capacitors, said spark-gap devices having ignition means for causing said spark-gap devices to simultaneously discharge said capacitors through said load for jointly producing a shock current therein, a voltage system connected directly parallelto said load and parallel to said capacitor means and'i'ncluding a voltage source,

control means interposed between said voltage source and said load and connected said ignition means to impress the voltage of said voltage source'upon the load in leading time relation to ignition of saidspark-gap devices, said voltage source having relative to said load a polarity opposed to the voltage polarity ofsaid capacitors.

4. A shock-current generator, comprising a load con- V stituted by a discharge vessel, a rmultiplicity ofmain capacitors connected to said load in parallel relation to each other to serve as surge-current sources, current supply means for charging "said main ca'pacitors, spark-gap devicesinterposed between said load and said respective main capacitors and having ignition :means tor causing said spark-gap devices to simultaneously discharge said main capacitors through said load for jointly producing a shock current therein, a voltage source comprising an auxiliary capacitor connected to said load, control means interposed between said auxiliary capacitor and said load and connected with said ignition means to impress the voltage of said auxiliary capacitor upon the load in leading time relation to ignition of said spark-gap devices, the voltage of said auxiliary capacitor when charged being higher than that of said main capacitors and having relative to said load a polarity inverse to that of said main capacitors.

5. In a shock-current generator according to claim 3, said voltage source comprising a plurality of auxiliary capacitors mounted in symmetrical relation to said load and connected in parallel to each other, and circuit means for charging. said auxiliary capacitors.

6. Ina shock-current generator according to claim 1, said control means having dififerent time constants relative to switching of said current sources and said voltage source respectively so as to render said voltage effective at said load terminals prior to switching of said current sources, the time difference being in the order of second.

7. A shock-current generator, comprising a load, a mul tiplicity of main capacitors connected to said load in parallel relation'to each other to serve as surge-current sources, current supply means for charging said main capacitors, spark-gap devices interposed between said load and said respective main capacitors and having ignition means for causing said spark-gap devices to simultaneously discharge said main capacitors through said load for jointly producing a shock current therein, a voltage source comprising auxiliary capacitor means connected in parallel to said'load, another spark-gap device interposed between said auxiliary capacitor means and said load and having ignition means for causing said auxiliary capacitor means to impress a voltage upon said load, the voltage of said auxiliary capacitor means having a polarity opposed to that of said main capacitors, an ignition pulse transmitter common to all of said spark-gap devices,

1 and conductors connecting saidtransmitter with said respective ignition means and having respectively diliersaid capacitors being spaced from said load, said sparkgap devices being disposed in proximity of said respecout wave-travelling periods whereby the pulse issuing from i said transmitter reaches said spark-gap device for said auxiliary capacitor means earlier than the other sparkgap devices. 1

8. A shock-current generator according to claim 1,

tive capacitors, and conductor means connecting said spark-gap devices with said load, said conductor means having between adjacent spark-gap devices a wave-travel constant in the order of 10* second.

10. A shock-current generator, comprising a centrally arranged load, a circular group of main capacitors radially spaced from said load and peripherally distributed about said load, current supply means for charging said capacitors, spark-gap devices serially interposed between said load and said respective capacitors and having ignition means for causing said spark-gap devices to simultaneously discharge said capacitors through said load for jointly producing a shock current therein, said spark-gap devices being located in proximity to said respective main capacitors, coaxial conductor means extending radially between said'respective spark-gap devices and saidload and electrically connecting said maincapacitors in parallel relationto each other across said load, a source of voltage comprising a plurality of auxiliary capacitors mounted centrally of said circular group and connected in parallel to each other across said load, the voltage of said auxiliary capacitors having a polarity opposed to the voltage polarity of said main capacitors, additional spark gap devices serially interposed between said load and said auxiliary capacitors respectively and having ignition means for applying said voltage to said load, an ignition pulse transmitter, conductor means connecting said transmitter with said ignition means of all of said spark-gap devices, said conductor means having between said transmitter and said spark-gap devices of said auxiliary capacitors a wave-travel time constant shorter than between said transmitter and said other spark-gap devices, the difference being in the order of 10 second, and said coaxial conductor means having between peripherally adjacent main capacitors a wave-travel time constant in said same order of magnitude.

References Cited in the file of this patent UNITED STATES PATENTS" 1,000,397 Galletti Aug. 15, 1911 

1. A SHOCK-CURRENT GENERATOR, COMPRISING A MULTIPLICITY OF SURGE-CURRENT SOURCES, LOAD TERMINALS TO WHICH SAID CURRENT SOURCES ARE CONNECTED IN PARALLEL RELATION TO EACH OTHER WITH THE SAME RESPECTIVE VOLTAGE POLARITIES, NORMALLY OPEN CURRENT CONTROL MEANS HAVING RESPECTIVE SPARK GAPS INTERPOSED BETWEEN SAID RESPECTIVE CURRENT SOURCES AND SAID TERMINALS AND HAVING IGNITION MEANS FOR SIMULTANEOUSLY IGNITING SAID SPARK GAPS TO SIMULTANEOUSLY SWITCH SAID CURRENT SOURCES ONTO SAID LOAD TERMINALS TO JOINTLY PRODUCT A SHOCK CURRENT WHEN A LOAD IS CONNECTED TO SAID TERMINALS, A VOLTAGE SOURCE CONNECTED ACROSS SAID LOAD TERMINALS, SAID CONTROL MEANS COMPRISING SWITCHING MEANS INTERPOSED BETWEEN SAID VOLTAGE SOURCE AND SAID ACROSS SAID TERMINALS WHEN SAID CURRENT SOURCES ARE BEING SWITCHED ONTO SAID TERMINALS, SAID VOLTAGE SOURCE HAVING AT SAID TERMINALS A VOLTAGE POLARITY OPPOSED TO THAT OF SAID CURRENT SOURCES. 